The present invention relates generally to radar and Electronic Warfare (EW) systems, in particular to high power transmitters used in these systems.
This application is related by subject matter to the application Ser. No. 10/097,408 entitled xe2x80x9cArray Antenna Beam Steering Architecturexe2x80x9d, filed in the name of inventors Martin J. Apa, Joseph Cikalo, William L. High and Mitchell J. Sparrow.
Electronic Warfare (EW) generally relates to military action involving the use of electromagnetic and directed energy to control the electromagnetic spectrum or to attack the enemy. The three major subdivisions within EW are Electronic Attack, Electronic Protection, and Electronic Support. Electronic Attack (EA) is the division of EW involving the use of electromagnetic or directed energy to attack personnel, facilities or equipment with the intent of degrading, neutralizing or destroying enemy combat capability. There is a great need for transmitters used in an EW system to be small in size, low in weight, and able to carry many watts/cubic inch. In addition, there is often a need in EW systems for a higher power transmitter that is also polarization agile.
One objective of an EW system may be to produce a jamming signal (e.g. false targets) in a threat radar receiver that is much greater in amplitude than that of the radar signal reflected by the target aircraft, with the appropriate polarization. The availability of advanced power amplification technologies makes it possible to develop high power transmitters with the above characteristics.
The basic architecture of such a transmitter is an active aperture antenna consisting of a large number of elements. Though the output power of each antenna element is a relatively low level, a high power Radio Frequency (RF) signal is obtained by combining the individual signals in space. To attain the highest power levels, a phase focusing technique is employed. Each element is tuned to produce a signal with the appropriate phase in order to spatially combine. However, phase focusing also produces a narrow beam antenna. Consequently, a beam steering network is used in order to radiate the maximum transmitted signal in a desired direction. Generally, a beam steering network may comprise a network having variable phase shifters, time delay elements or fiber optic delays with an external processor and drivers to adjust them.
Conventionally, the phase shifters are inserted at the output terminal of the system""s power amplifiers, just prior to feeding the RF radiators. A significant drawback of this architecture is that a large amount of RF power is dissipated in the phase shifters placed after the power amplifiers. This reduces the efficiency of the system and requires additional cooling system capability. Moreover, dissipation of a large amount of RF power in such an architecture generally requires use of large, less reliable high power phase shifters that must be capable of handling high RF power levels. The requirement for large size phase shifters makes such transmitter systems used in EW equipment more bulky, less accurate, and less agile. These are significant drawbacks.
Also, when such a transmitter is installed on an mobile vehicle, such as an aircraft, it is necessary that as the mobile vehicle changes direction, the phase shift entered by the beam steering network is also changed. To effectively focus the narrow beam in the direction of the threat radar, it is important to monitor the direction of the incoming signal from the threat radar and adjust the phase shift effected by the beam steering phase shifters. In open loop systems, typically no adjustment is provided regarding the difference between the direction of the incoming signal and the direction of the transmitted signal. This can undermine the effectiveness of the radar jamming capability.
Other problems and drawbacks also exist.
An embodiment of the present invention comprises a polarization agile transmitter module with a closed loop architecture. The polarization agile transmitter module includes a beam steering phase shifter module, a power amplifier module, an antenna module, a transmit polarimeter, a receive polarimeter, a null adaptive tracker, and a direction finding phase shifter module, where the beam steering phase shifter module is located before the power amplifier module.
According to another aspect of the invention, an electronic counter-measure (ECM) signal is inputted into the beam steering phase shifters.
According to another aspect of the invention, the direction finding (DF) phase shifter module measures the difference in the direction of the signal received by the antenna module and the direction of the signal transmitted by the antenna module.
According to yet another aspect of the invention, the phase shift entered by the beam steering phase shifter module is changed based upon the difference in the direction of the signal received by the antenna module and the direction of the signal transmitted by the antenna module, as measured by the DF phase shifter module.
According to another aspect of the invention, the receive polarimeter measures the polarization parameters of the signal received by the antenna module.
According to yet another aspect of the invention, the transmit polarimeter adjusts the polarization of the signal transmitted by the antenna module based on the feedback received from the receive polarimeter regarding the polarization of the signal received by the antenna module.
According to another aspect of the present invention, multiple polarization agile transmitter modules are used with an array of antenna modules.
According to another aspect of the present invention, a summing network is provided with multiple polarization agile transmitter modules for summing the signal received by each of the multiple modules.
According to another aspect of the present invention, a direction finding (DF) receiver is provided for monitoring and processing of the directional information regarding the received signal.
According to yet another aspect of the present invention, a beam scanning module is provided to display the output signal from the DF receiver.
Accordingly, it is one object of the present invention to overcome one or more of the aforementioned and other limitations of existing polarization agile transmitter systems.
It is another object of the present invention to provide an efficient polarization agile transmitter using low power phase shifters.
It is yet another object of the present invention to provide a polarization agile transmitter that solves or mitigates the problems associated with the requirement of high power beam steering phase shifters.
It is another object of the present invention to provide a polarization agile transmitter that is smaller, lighter and more reliable.
It is yet another object of the present invention to provide a polarization agile transmitter capable of adjusting the direction of the transmitted signal based on the direction of the incoming signal.
It is yet another object of the present invention to provide a polarization agile transmitter capable of adjusting the polarization of the transmitted signal based on the polarization of the incoming signal.
The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute part of this specification, illustrate several embodiments of the invention and, together with the description, serve to explain the principles of the invention. It will become apparent from the drawings and detailed description that other objects, advantages and benefits of the invention also exist.
Additional features and advantages of the invention will be set forth in the description that follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the systems and methods, particularly pointed out in the written description and claims hereof as well as the appended drawings.